Form: Iatrogenic CJD (iCJD)Cause: Contamination through brain surgery, corneal transplant, dura mater graft, or growth hormoneDistinguishing Features: Age at onset depends on the age at exposure and on the incubation time. Clinical and pathological features are often indistinguishable from sCJD. Growth hormone cases show plaques.

Form: Variant CJD (vCJD)Cause: Exposure to BSE through consumption of infected beef or blood or plasma transfusionDistinguishing Features: With exposure to BSE, younger onset and longer duration than sporadic CJD. Psychiatric symptoms often seen at disease presentation. Distinctive “daisy” plaques upon tissue examination. For blood or plasma transfusion, age at onset depends on the time of exposure.